Students will work in two broad research areas. In the first project, structure and functions of the enzyme glycyl-tRNA synthetase will be investigated in order to provide information concerning basic molecular mechanisms of protein synthesis. This work will concentrate particularly on the role placed by dissimilar subunits in the recognition and activation of tRNA and ATP. Affinity labeling reagents will be employed to probe the enzyme's recognition sites and modified peptides isolated to locate essential amino acid residues in the active site of the enzyme. Subsequent studies will be directed at a closely related enzyme, phenylalanyl-tRNA synthetase. Computer analysis will compare amino acid sequences so identified with those of other aminoacyl -tRNA synthetases to better understand how these enzymes as a group accomplish their essential role in vivo. In the second project, the proteins forming the extracellular matrix of sea urchin embryos following fertilization will be investigated. By purifying the protein components of the hyaline layer and the fertilization envelope, we hope to provide an understanding of the molecular mechanisms of cellular organization in the embryo and the manner in which the block to polyspermic fertilization is accomplished. A major goal of this work is to provide information regarding the amino acid sequence of three proteins already isolated by students in the laboratory. This work aims to correlate amino acid sequences of the proteins with DNA sequences of hyalin-associated proteins presently being completed in other laboratories. Together, these data can serve to understand how the three proteins are related to one another and to other calcium-binding and extracellular matrix protein as well as how these proteins are regulated developmentally and how they perform their essential biological role. The primary goal of this project is to provide a scientific environment which gives these students the opportunity to succeed as young scientists and an atmosphere which supports and encourages academic involvement and achievement. Students form our laboratory have established a strong record of accomplishment. Of the fifty-nine students who have completed projects since 1980, 44% have entered graduate or professional programs.